The epidemic of thyroid cancer in the United States: the role of endocrinologists and ultrasounds

Abstract

Background: The incidence of thyroid cancer has increased at an alarming rate in both men and women in the United States. The etiology of this epidemic is unclear. We tested the hypothesis that a significant component of this epidemic is due to increased detection of occult disease. We examined whether the density of endocrinologists and general surgeons as well as employment of cervical ultrasonography were factors associated with this epidemic.

Methods: Thyroid cancer incidence rates by states were obtained from the United States Cancer Statistics 1999-2009 reported by the National Program of Cancer Registries. The densities of endocrinologists and general surgeons and the employment of cervical ultrasonography were calculated on a statewide basis and correlated with the incidence of thyroid cancer.

Results: Age-standardized incidence rates of thyroid cancer have increased in every state in the United States. Significant regional variations were noted, with the highest incidence rates in the northeast and the lowest in the south. The incidence rates were significantly correlated with the density of endocrinologists (r = 0.58, p<0.0001 for males; r = 0.44, p = 0.0031 for females) and the employment of cervical ultrasonography (r = 0.40, p = 0.0091 for males; r = 0.36, p = 0.0197 for females). Both the density of endocrinologists and general surgeons and employment of cervical ultrasonography could explain 57% of the variability in state-level incidence for males and 49% for females.

Conclusions: These data offer evidence to suggest that the epidemic of thyroid cancer is due to increased detection of a reservoir of previously occult disease. The increased detection of thyroid cancer results in therapeutic interventions including surgery and radioactive thyroid treatment that may be of limited benefit.

FIG. 1.

Trends in age-standardized thyroid cancer rates by gender and state for the time period 1999–2009: (A) male; (B) female.

FIG. 2.

Age standardized incidence rates of thyroid cancer by U.S. state for the time period 2005–2009.

FIG. 3.

Density of endocrinologists by U.S. state (number of endocrinologists per 100,000 population).

FIG. 4.

Density of general surgeons by U.S. state (number of general surgeons per 100,000 population).

FIG. 5.

The counts of neck ultrasonography per 100,000 commercially insured population for the period 2005–2009.